The present invention relates generally to an improved connection between the center plate and fan blades of an impeller wheel and more specifically to two laterally spaced prongs on the base plate being respectively tightly received in two laterally spaced, wedge shape receptacles in a notch within each fan blade to form a frictional and mechanical connection therebetween.
One common system used to circulate air or other fluids includes a motor that rotates a shaft to which an impeller is attached. An exemplary center plate fan assembly, known as an impeller wheel or squirrel cage impeller, is shown in FIG. 1.
Impeller wheels typically include a hub, a center plate affixed to and extending radially outwardly from the hub and a plurality of fan blades connected to the center plate. The fan blades are usually equally circumferentially spaced about the center plate to form a xe2x80x9csquirrel cagexe2x80x9d assembly. These fan blades are connected to the radially outer edge of the center plate.
The prior art connection between the center plate and fan blades is shown in FIG. 5 and includes a rectangular or hourglass shape notch I in the radially lower edge 2 of each of the fan blades 3. The connection also includes bifurcated prongs 4A and 4B on the radially outer portion of the center plate, indicated generally at 6. During assembly, the prongs 4A and 4B are forced into the blind end corners of the notch 1 in fan blades 3 to create a frictional and mechanical connection joint. This joint is formed by the center plate prongs being deformed as they are respectively forced into the corners and along the opposed sides of the fan blade notch 1. As is apparent from FIG. 5, the ends of the prongs 4A and 4B engage the end of the notch I and the laterally outer sides of the prongs have limited engagement with the respective opposed sidewalls of the notch 1.
The present invention includes a notch that has a tongue provided on and extending inwardly from a portion of the end wall of the notch. The tongue cooperates with the end wall and sidewalls of the notch to form two wedge shaped, laterally spaced receptacles. The resultant notch has a generally M shaped configuration, with the wedge shape receptacles extending at equal but opposite angles relative to the centerline of the center plate.
The wedge shaped receptacles in the notch tightly receive the prongs on the center plate to form the connection joint. The wedge shaped receptacles are configured to provide a contact and interference fit with the center plate prongs inserted therein. The prongs deform as they are forced into the receptacles, and both sides of the prongs contact and interfere with the sidewalls of the wedge shaped receptacle. This engagement of the prongs on both sides thereof with the wedge shaped receptacles creates additional mechanical locking and friction not obtainable with the prior art rectangular or hour glass shaped notch, since the engagement on those notch designs is only on one side of the prong.
It is an object of the present invention to provide an improved connection between a plate and a blade.
It is a further object of the present invention to improve the connection between the center plate and fan blade of an impeller wheel to enhance its resistance to torsional operating forces.
It is yet another object of the present invention to provide a fan blade notch having two laterally spaced wedge shaped receptacles therein, which respectively tightly receive two laterally spaced prongs on the center plate of an impeller wheel. Both sides of each prong contact the converging sidewalls of the wedge shape receptacle to form an enhanced mechanical and frictional connection.